If the EU doesn’t succeed in fairly distributing refugees coming from war-torn countries, the passport-free Schengen zone will need to be reviewed, German Chancellor Angela Merkel said Monday after Hungary asked Berlin to “clarify” the legal situation on refugees.

"If we don't succeed in fairly distributing refugees, then of course the Schengen question will be on the agenda for many," Merkel said at a conference in Berlin.

Austria has tightened its eastern borders, just days after the bodies of 71 refugees were found in a truck on a highway.

"We will [carry out checks] for an undetermined period of time at all important border crossings in the eastern region, looking at all vehicles that have possible hiding places for trafficked people," Austrian Interior Minister Johanna Mikl-Leitner told ORF radio Monday.

She said that the checks were not traditional border controls, adding that the country was within its legal rights.

Hungarian police said Sunday that a fifth person, a Bulgarian citizen, had been arrested in connection with the deaths. Four others – three Bulgarians and one Afghan citizen – have also been arrested.

The suspects face up to 16 years in prison for people trafficking in Hungary, as well as murder charges in Austria.

After the incident that claimed lives of 71 refugees in an abandoned truck near the Hungarian border, Austrian authorities stepped up security on the border and intensified checks on the country’s roads, stopping hundreds of refugees and arresting five traffickers.

LISTEN MORE:

Hungary turns to Germany

Meanwhile, Hungary has asked Germany to clarify the legal situation surrounding illegal migrants traveling within the European Union, a Hungarian government spokesman told MTI on Monday.

Andras Giro-Szasz said that under the EU's Schengen rules, migrants can only leave Hungary with valid travel documents and a visa from their destination country.

But Giro-Szasz says that Germany has shown a more permissive stance towards illegal immigrants arriving from Syria, adding that the news has “boosted hopes” among migrants.

"In order to end the non-transparent and adverse conditions we ask Germany to clarify the legal situation," he said.

Meanwhile, German government officials took to Twitter on Monday to deny claims that there are “special trains” carrying migrants to Germany from Hungary, adding that asylum seekers arriving in Hungary must be registered there first.

"No, there are no special trains," Chancellor Angela Merkel's spokesman Steffen Seibert wrote. "People who come to Hungary must register and seek asylum there."

On Monday, Hungary allowed migrants to board at least four trains heading from Budapest to Vienna or German cities.

One of the trains was stopped by Austrian authorities at the border with Hungary due to “overcrowding” and “safety concerns.” Austrian police tried to check whether any of the migrants on the train had already asked for asylum in Hungary. The police spokesperson said that only those who had not done that could be allowed through in accordance with the EU regulations, as reported by Reuters.

Eventually, with few police officers and border officials present at the crossing, Austrian authorities bowed to the pressure of the crowd and allowed the train to move on apparently with all of the passengers on board, although it had been previously stuck in the Hungarian border town of Hegyeshalom for several hours, Reuters reported.

With the trains carrying migrants arriving in Vienna, the city’s police spokesman announced that the refugees were allowed to stay in Austria for two weeks in order to decide if they were going to ask for asylum in the country. Those who would not do it would be returned to the last transit country – in this case, to Hungary.

However, many migrants rushed to board trains to Germany right after arriving to Vienna with Austrian police refraining from interference, a witness told Reuters.

The trains with the refugees started to arrive to German cities on Monday evening. According to German police, the first train that came to Munich carried around 200 migrants. German authorities have not conducted any checks so far.

“Thank God nobody asked for a passport ... No police, no problem,” Khalil, 33, an English teacher from Kobani in Syria, who arrived in Munich, told Reuters.

Around 10,000 are believed to have crossed into Hungary from Serbia in the last week alone. In total, about 150,000 migrants have been detained already this year in Hungary – more than triple the figure recorded for all of 2014.

Hungary has constructed a 4-meter-high fence along its border with Serbia and is working to build another one. The move has been criticized by French Foreign Minister Laurent Fabius.

"Hungary is very severe. Hungary is part of Europe. Europe has some values and it doesn't respect these values. Like this razor wire barrier they built,” Fabius told Europe 1 channel on Sunday.

Hungary rebuffed the criticism, as it plans to continue its policy and tighten security with new measures. It is going to create holding camps near its border with Serbia as well as potentially use the army to help the police cope with the situation along the border, provided that this move gets the parliament’s backing.

The country also plans to toughen the migration laws by imposing stronger penalties for illegal border crossings or damaging the fence along the Serbian border, thus allowing authorities to expel the migrants that violate the new regulations.

Escalating crisis

As refugees from Syria, Iraq, Afghanistan and other nations continue to pour into Europe in staggeringly high numbers, Central European leaders plan to meet at the end of this week to discuss the crisis, Slovak Prime Minister Robert Fico said Monday.

Fico said the meeting would take place on Friday or Sunday, and would include the Czech Republic, Poland, Slovakia, and Hungary.

EU interior ministers are also planning to conduct emergency talks to discuss the crisis, which officials say is the worst since World War II.

"The situation of the migration phenomena outside and inside the European Union has recently taken on unprecedented proportions," the Luxembourg government, which holds the EU's six-month rotating presidency, said in a statement Sunday.

The talks, which will take place on September 14 in Brussels, have been scheduled “to assess the situation on the ground, the political actions under way and to discuss the next steps in order to strengthen the European response,” the Luxembourg statement said.

The announcement followed calls for talks from Germany, France, and Britain earlier on Sunday.